1. Technical Field
The present invention relates to a motor control device, a fluid ejection device, and a motor control method.
2. Related Art
As an ink jet printer, there is a type of printer available for sheets having an A2 or larger size. In many cases, the large-sheet ink jet printer uses a so-called roll paper (hereinafter, the so-called roll paper that is a wound roll is referred to as a roll, and a portion pulled from the roll is referred to as a sheet) in addition to cut papers. Pulling a sheet from a roll is typically performed by a paper feed motor (PF motor). Here, the PF motor is controlled and driven by PID control. As the printer using the roll, a printer is disclosed in JP-A-2007-290866. As the printer which enables the PID control, printers are disclosed in JP-A-20006-240412, JP-A-2003-79177, and JP-A-2003-48351.
The roll in the large-sheet printer is heavy, and a load exerted when a sheet is pulled from the roll is high. Accordingly, when only the PF motor is driven, there is a possibility that the paper is torn up. Therefore, models in which a roll motor for rotating the roll is provided and driven together with the PF motor to pull a sheet have been developed.
Here, as the sheet is pulled from the roll, the diameter and weight of the roll are changed. Accordingly, in the case where a constant output (current) is given to the roll motor, as the diameter and weight of the roller are changed, tension between a transport roller pair rotated by the PF motor and the roll is significantly changed. In addition, for example, in the case where the weight of the roller is reduced and becomes very low, there is a possibility that tension is hardly exerted between the transport roller pair and the roll, and the paper becomes loose. When the change in the tension as described above occurs during printing of the sheet, it may affect the print quality.